Meta-analysis of the risk factors of breast cancer concerning reproductive factors and oral contraceptive use

Abstract

The authors performed a meta-analysis of casecontrol studies that addressed whether reproductive factors and oral contraceptive use were associated with breast cancer by searching the MEDLINE, PubMed, Proquest, Embase, ScienceDirect, African Healthline, BMJ Health Intelligence and Chinese Periodical net databases for all English-language and Chinese-language papers published from A total of 15 studies calculating pool ORs indicated that menopausal age > 50 yr [odds ratio (OR), 1.39; 95% confidence interval (CI), 1.22-1.57] and oral contraceptive use (OR, 2.12*, "*": summary OR was adjusted; 95% CI, 1.24-3.62) were correlated with the increase in breast cancer risk while the summary OR based on number of full-term pregnancies≥1 (OR, 0.63*; 95% CI, 0.60-0.68) and breast-feeding (OR, 0.76; 95% CI, 0.64-0.90) indicated no association with breast cancer risk. The correlation was statistically significant. Menopausal age > 50 yr and oral contraceptive use are positively correlated with an increase in breast cancer risk while breast-feeding and number of full-term pregnancies≥1 are protective factors.

<p>Epidemiological characteristics of and risk factors for breast cancer in the world</p>

“…The age of menopause over 50 years is associated with an increased risk of breast cancer 31,44,50. The results of a case– control study also confirmed the association between older age in menopause and the incidence of breast cancer (OR, 2.43; 95% CI, 1.2–4.9) 36…”

“…Based on the results of a case–control study, the use of oral contraceptive pill is associated with an increased risk of developing breast cancer (OR, 9.50; 95% CI, 3.38–26.7) 43. This result was confirmed in other studies 44,49,50. Meanwhile, according to the findings of a study by McDonald and coworkers,65 which was conducted on 35- to 64-year-old women, current (RR, 1; 95% CI, 0.8–1.3) or previous use (RR, 0.9; 95% CI, 0.8–1) of contraceptive pills was not associated with an increased risk of developing breast cancer.…”

“…A study indicated that every childbirth reduces the risk of PR+ and ER+ cancers by up to 10% (RR per birth, 0.89; 95% CI, 0.84–0.94), and women who were older at their first childbirth had a 27% increased risk of developing breast cancer (RR, 1.27; 95% CI, 1.07–1.50) 52. The results of the studies showed that full-term pregnancy is considered as a protective factor 50,51. The results of a study showed that breast cancer is more likely to occur in nulliparous women than women who have more than three children (OR, 1.98; 95% CI, 1.12–3.49) 53.…”

“…Breast feeding is a protective factor against breast cancer, and many researchers have pointed to the role of lactation in breast cancer prevention 31,86. Based on the results of various studies, the length of lactation is associated with breast cancer 43,44,50,87. The protective effect of lactation increases with increasing duration of lactation 44.…”

PI3K/AKT/mTOR Signaling Pathway in Breast Cancer: From Molecular Landscape to Clinical Aspects

“…Full-term pregnancy is a protective factor against breast cancer [ 20 , 21 , 22 ], with nulliparous women having an increased risk for breast cancer [ 23 ]. On the other hand, during the first pregnancy, important and permanent changes in the mammary gland cells occur: the glandular cells have a longer cell cycle and a prolonged G1 phase (Gap 1 phase)—it is the phase that allows DNA to repair.…”